Transmission of pictures of moving objects.



A. SINDING-LARSEN. y TRANSMISSION OF PICTURES 0F MOVING OBJECTS.

APPLICATION F|LED1uNE1o,1911.

1 1 75, 3 1 3 Patented Mar. 14, 1916.

2 SHEETS-SHEETA l.

Figi.

A. SlNDlNG-LARSEN.

TRANSMISSION OF PICTURES 0F MOVING OBJECTS.

APPLICATION FILED JUNE I0. 19H.

i1, 1 75,3 1 3. Patented Mar. 14, 1916.

2 SHEETS-SHEET 2.

Fig. 7.

""WM/ Qf maw 6 210 ZU@ l A l" L UNITED STATES PATENT OFFICE.

ALF SINDING-LARSEN, OF CHRISTIANIA, NORWAY, ASSIGNOR 0F ONE-HALF T0JOHAN HENRIK -LABE LUND, OF CHRISTIANIA, VNOIWVAY.

Specification of Letters Patent.

Patented Mar. 14, 1916.

Application led June 10, 1911. Serial No. 632,410.

To all whom t may concern. 'p

Be it known that I, ALF SINDING-LARsEN, a subject of the King of Norway,residing at Christiania, Norway, have invented certain new and usefulImprovements in and Relating to the Transmission of Pictures of MovingGbjects; Vand I do hereby declare that the following is a full, clearAand exact description of the same.

My invention relates to the art of transmitting over long distancespictures of moving objects, and consists in improvements in the methodor system as well as in the means and in the combinations of devices forcarrying out the invention. In the devices hitherto proposed fortransmitting pictures through conductors a principle common to all ofthem is, that the picture to be transmitted is decomposed into a seriesof points or elements by devices performing two linear movementsperpendicular to each other, said elements being successivelytransmitted to the receiver, in which, by corresponding linearmovements, the pictures are recomposed. This necessitates two absolutelynchronous movements at the transmitter and the receiver. In thegraphical transmission of pictures (for instance according to the Kornssystem) in which the duration of each movement is not limited, it isnotdifiicult to establish such synchronism, but in the transmission ofmoving pictures, where every light point or picture element has to berepeated before the light impression on the eye has ceased, (between onetenth and one hundredth part of a second).which requires a very rapidperformance of each single movement, such a motion system is verydifficult to accomplish. A prior inventor (British Patent 27570/07) hastried to overcome this difficulty by making use of a picture decomposedin the transmitter, comprising two rotary polyhedral mirrors the axes ofwhich are perpendicular to each other and which rotate at differentspeeds. The recomposing device in the receiver, however, does notconsist'of a similar mirror system with a corresponding motion, scheme.which would have been impracticable on account of the absolute accuracy`rof synchronism necessary), but itis proposed to effect the recomposingof the picture in these systems by means of electrical current impulses,created hv the rotating systems, which impulses vcause synchronouslinear movements in oscillographs, especially in the so called Braunstubes,- known from the scientific study of electrical waves. In otherwords, in these systems synchronous movements are sought to beestablished between devices of wholly different natures, a scheme whichmay be considered practically impossible to realize. The use ofpolyhedral mirrors for the purpose is moreover, in itself,disadvantageous, as each mirror4 is only partially utilized, the mirrorsentering the field of rays successively, and again successively leavingsaid field. Another drawback is that the picture elements may becomeintermiXed, as a reflection may take place simultaneously from twosurfaces of the polyhedron.

In contradistinction to this old system my invention consists in asystem for the transmission over long distances of pictures of movingobjects in which an absolutely synchronous motion is practicallyrealized by arranging the transmitter and the receiver in such mannerthat the movements required for the decomposing devices and thoserequired for the recomposing devices are of the same character.

One important point in my invention isthat the decomposer at thetransmitting station and the. recomposer at the receiving station bothhave a double oscillating motion, that is to say, they performoscillations in two different planes, and that the synchronism of theseoscillations is insured by the action of oscillating bodies having freevibration and kept in motion by a common source of driving force.

Having indicated the nature of my invention as regards the principleemployed for enabling me to Secure a synchronous action of thedecomposing and the recomposing devices, I shall now explain someexamples of how the invention as a whole may be carried out,'andf.describe some of the devices which I have-,made use of. in order toprove the possibility of practically utilizing my invention. An imageofthe object is taken'up by a kind of camera, in which, however, theimagedoes not fall directly upon the rear image surface, or .focalplane, but in which a mirror is mounted between such plane and theobject lens, said mirror reflecting .the light to another mirror fromwhich the light finally falls upon the image surface. These two mirrorsare associated with tuning forks or like freely vibrating devices,having different frequency of vibrations.Y The axes vso of oscillationof said mirrors may be perpendicular to one another, or form some otherangle, While their planes should be parallel when in the middleposition. These tuning forks, one of which may have a vibrationfrequency of N for instance 100 in a second, and the other a frequencyof N2 or 10000 in a second, may now be kept in steady motion by means ofa suitable electromagnetic arrangement. By means of this device everyvpoint of the image formed is in its turn transmitted to one and thesame point on the image surface. At this point a light opening isarranged, and immediately behind this opening is the light receivingdevice which transmits the light to the receiver.

The receiver is constructedv in a manner quite similar to thetransmitter. It comprises a device emitting through a small lightorifice the light coming from the transmitter, or emitting the lightfrom a local light source, the light given od through the light-orificevarying in intensity in accordance with the simultaneous intensity ofthe light passing through the light orifice of the transmitter. Thevariable light po-int thus formed in the receiver is looked upon througha system of reiiectors corresponding to that of the transmitter, andoscillating synchronously with this latter system.

For transmitting the pictures-directly I make use of a. narrow tubeWwith strongly reectino' inner surfaces, which tube is arranged.j withits rear opening behind the light orifice in the transmitter. The tubeis preferably made of silver, gold, copper or other metal having arefraction coefficient lower than that of air. The optical systemforming the image is arranged in such a manner that the rays forming theindividual image points cross one another at a very acute angle. By thisIam enabled to cause the light taken up in the mouth of the tube to betransmitted through the tube without being materially weakened in its.passage to the other end of the tube and vthe image surface ofthereceiver. In order to maintain lrhe greatest possible reiiecting angl',`of the light rays during passage through the tube, the tube should havea very small sectional area and its curves or bends be of the greatestpossible radius.

The synchronous movement of the mirrors is effected by coupling inseries the electromagnets serving to keep the mirrors moving. The sametube that transmits the light rays may serve as conductor for theelectric current. All these oscillating parts may be made to work in avacuum in order to avoid disturbing noise and possible disadvantagesresulting from air damping.

When the transmission'of the picture is effected directly, that is, Whenthe light A'is conducted through reecting tubes, these latter may bekept filled with a gas adapted to preserve the reflecting surfaceagainst oxidation, such for instance, as hydrogen. The tube may also beevacuated.

To insure constant andcomplete uniformity between the oscillations ofthe tuning forks and of the mirrors associated with said forks, I makeuse of the following -arrangement: The electromagnets actuating thetuning forks in the transmitter and receiver are coupled in series andare thus driven from a common source of current; while the quicklyoscillating tuning forks or the magnet armatures mounted upon them areunpo-larized, so that the direction of current in the electroma'gnethaving a very soft iron core is of no consequence. The slowlyoscillating tuningforks or their armatures are polarized in such a.manner that the direction of oscillation is dependent upon the directionof current in the magnet. A third tuning fork arranged in thetransmitter or receiver and having the same frequency of vibration asthe abovementioned slowly oscillating ones, serves to control therotation of a commutator inserted in the battery circuit, which by meansof suitable segment arrangement transforms the direct current intoalternating current, whose periodicity is in accordance with theperiodicity of the slowly oscillating tuning forks. It is obvious thatthe slowly oscillating, polarized tuning fork arranged in the receiverand transmitter when acted upon by an alternating magnetic field of itsown periodicity produced by this alternat- Ying current, is compelled tomaintain quite consonant and coincident oscillations. And it is alsoquite clear that the quickly oscillating tuning forks in the transmitterand receiver which are acted upon by one and the same interruptedcurrent corresponding with their periodicity of oscillation are alsocompelled to maintain quite coincident oscillation. The rotationcontrolled by means of said third tuning fork may also vact to directlyproduce the alternating current necessary, so that a battery may besuperiuous. For these arrangementa'as well as for those above-described,other bodies with a free vibration or self-oscillating capacity may beemployed, instead of tuning forks. In vthe transmitter and in thereceiver an electromagnet may be employed for the purpose of drivingboth tuning forks. The conductor or conductors emploved for thetransmission of pictures may also be used for the purpose of telephoningor transmission of telegrams.

I shall now describe some forms of apparatus used by me in carrying outmy invention.

Referring to the drawings, in which like p arts are similarlydesignated-Figure l is a diagram of motion. Fig. 2 is a side y view of a.transmitter and a receiver illustrating means for carrying out theinvention. Fig. 3 is a longitudinal section on an enlarged scale throughthe transmitter. Fig. 4L is a. detail showing a cross section throughone of the mirrors. Figs. 5 and 6 are details. Fig. 7 is a diagrammaticperspective view of a generator for interrupted alternating cur-rents.Fig. 8 is a current diagram. Fig. 9 shows a vmodification of' the mirrorarrangement.

Reference being had to Figs. 2-6, T represents the transmittingapparatus and R the receiver; they are supposed to be connected by areflection tube 5. 1 is the object lens of the receiving station camera,in which is placed two mirrors, 2 and 3; the mirror 2 oscillates veryfast on an vaxis perpendicular to the plane of the drawing, while themirror 3 oscillates more slowly on an axis lying in the said plane andis perpendicular to the axis of oscillation of the mirror 2. By thesemeans the elements of the image formed-by the lens 1 are in successionfolle-wing a continuous zigzag line, transferred to the focus of a lens4 placed in the opening of a reection tube 5, said lens parallelizingthe rays which meet the image point. In the receiver two similar mirrors7 and 6 oscillating synchronously with the mirrors 2 and 3 respectively,thro-w the train of rays emerging from the reflection tube to the eye ofthe observer as indicated, or to the object lens of a camera o-rprojection apparatus. The synchronous vibration of the respective pairsof mirrors is insured by means of the tuning forks and is maintained bymeans of electromagnets receiving current from the same source; thiscurrent may, for one of the pairs of mirrors, be an interrupted current,and for the other pair an alternating current, or it may besimultaneously interrupted and alternating, in which case it is notnecessary to have a separate circuit fo-r each pair of mirrors. Thebreaking or the alternation of the current for each pair of` mirrorscorrespo-nds with the frequency of the freevibration of the mirrors.This principle of resonant adjustment of the oscillating systems isfo-und to be an absolute condition for obtaining the synchronismnecessary for the correct transmission of the pictures; it enables mealso to have these movements established with a minimum of power, a factwhich is of no little importance. But the greatest advantage of thesystem is that the synchronism is in this manner self 'adjusting,because if the mirrors are by some outer force brought out of theirregular motion, they will immediately, when left to themselves, reassumetheir synchronous motion. The system therefore enables me to control anunlimited number of stations from a common central. K

In the drawing I have shown two sets of mirrors in each station. I mayalso make use of any other means for decomposing and recomposing thepicture in the manner described. The main feature of this part of theinvention being that the oscillatory movements used for thedecomposition and recomposition of the picture are tuned so as to be inresonance with the free vibration of the swinging bodies.

The rapidly swinging mirrors 2 and 7 may suitably be driven byinterrupted current supplied to electromagnets with unpolarizedarmatures, and the mirrors 3 and 6 may be driven by alternating currentby means of electro-magnets the armatures of which are polarized. If thetransmitter and the receiver' are driven by interrupted direct current,and the light transmission is effected by means of the describedreflection tubes, it will be seen that only two electricconductors areneeded for the transmission of the picture, and as one of these may bethe reflection tube and the other the earth, no other connection thanthe tube is necessary between the two stations. I have found that a tubeof an inside diameter of 2 millimeters and an outside diameter of 3millimeters is Suitable. Instead of tubes I may make use of wires orstrings of a material of little light absorbent quality, or of tubesfilled with fluids of this nature. In o-rder that as little light aspossible shall be absorbed bv the walls of the tube it is preferablethat the lens 4 shall have a short focal length. l

The mirror 2 (see Fig. 3) may be made of iron, polished and silverplated on the front face and have its back fixed to a piano string 8which has a free swing or vibration. The tension of the string is soadjusted that a suitable free vibration frequency is secured by thecombined action of the mass of the mirror and the forces of torsion 0fthe string. The piano string may be so mounted that it is prevented fromhaving transverse vibration, which latter would disturb the picture. .Y

9 represents an electro-magnet creatinga field'in which: the mirror actsas an armature. The windings of the electro-magnet are connected with aninterrupted current circuit the frequency of-which corresponds with thefree vibration frequency of theA mirror.

The mirror 3 is pivoted on the pins 10, 10, and on its back is secured apermanent magnet 11, the poles of which extend into the fields createdby the alternating current magnets 12, 12. This mirror has arelativelyslow vibratory motion, the frequency of which is made to correspond withthe frequency of the alternating current by adjustment of its mass andof -a spring, which tends to keep it in its intermediate position.

For generation of an interrupted alternating current suitable for thepurpose of my having a distinct free vibration, and 22 a motor-drivencommutator giving off current Vto the brushes 23, 24C, connected inseries or in parallel With the transmitting and receiving apparatus androtated, preferably, so as to send current impulses in synchro nism withthe free vibration of the suspenders for the mirrors. The commutator 22is driven by a Weight operatedmotor governed by an escapement mechanismconsisting of an escapement Wheel 62 having pins 63 coperating With thedetent 64 carried by an arm of tuning fork 60 which is kept in vibrationby the magnet 6l. According to the frequency of the interrupterrelatively to the number of alternations caused by the commutator,current-curves o-f difterent form Will be obtained. If the frequency ofthe interruptions is greater than the frequency of the alternations, assupposed in the apparatus above described., the curve will be as shownin Fig. 8. Of course the number of variations in each positive andnegative part of the Wave Will be much greater than shown. In order toincrease the intensity of the light transmitted there may be arrangedtivo or more light-transmitting and light-receiving devices at thetransmitter and receiver, respectively, said. devices coperating Witheach other and transmitting simultaneously dierent points of thepicture, either directly .or .indirectly as described; of course caremust be taken that the said devices are placed at the same distance andin the same relative position to each other at both stations.

If the transmitter and receiver have great dimensions, it may beunsuitable to use mirrors of the above-described arrangement, be causethe air may have too great a retarding action on mirrors of greatdimensions swinging With great velocity. In such a case- I may make useof mirrors formed in sections like Window blinds or louvers, as shown inFig. 9. The sections, although having a very slight peripheral movement,Will perform the saine Work as a continuous mirror, having the sameangular motion. These mirrorsmove on their axes synchronously' and arevibrated by like means as described with respect to mirrors 2 or 3.

Instead of a lens, as shown in Fig. 5, I may use an arrangement such asthat shovvn in Fig. 6. The endY of the tube is in this case providedWith a mouth piece 14 having a polished conical inner surface. The raysentering the small orifice of this mouth piece Will be repeatedlyreflected, so as to finally take a direction about parallel to the axisof the tube. It is preferable that the light rays enter the tube at aslight angle, for example, not over 10.

I claim l. In the method of transmitting pictures of moving objects to adistance, the step which comprises forming an image of the object,breaking up the image into minor elements by oscillating reflectorshaving a freely vibrating suspension, and maintaining the vibration ofsaid suspension by imparting to said reflectors impulses in phase Withthe vibration of said suspension.

2. In the method of transmitting pictures of moving objects to adistance, the step Which comprises forming an image of the object,breaking up the image by `double re flection to oscillating reflectorshaving freely vibrating suspensions, and maintaining the vibration. ofsaid reflectors by imparting impulses thereto substantially insynchronism with the fundamental of the suspension.

3. In the method of transmitting pictures of moving objects, the stepWhich comprises forming an image, breaking up the image by vdoublereflection first to a rapidly oscila lating reflector vhaving a freelyvibrating suspension and thence to a slowly vibrating reflector alsohaving a freely vibrating sus pension, and maintaining the vibration. ofsaid suspensions and reflectors by imparting impulses theretosubstantially in synchronism `with their fundamental. n

4l. Mechanism for transmitting moving pictures, comprising a sendingstation and a receiving station, each station having mirrors to producedouble reflection, and a reflecting tube connecting the stations, saidmirrors having freely vibrating suspensions and means to produce amagnetic field for each mirror in synchronism With thevibrations of saidsuspensions.

Mechanism for transmitting moving pictures, comprising a sending stationand a receiving station, each station having tWo reflectors vibrating atan angle to .one another, freely vibrating suspensions for saidreflectors, and electro-magnetic means to maintain said mirrors invibration, and means to simultaneously send current impulses to saidelectro-magnetic means in synchronism with the vibrations of saidsuspensions..

In testimony that I claim the' foregoing as my invention, I have signedmy name in presence of tWo subscribing Witnesses.

Y ALF SINDING-LARSEN.

Witnesses: .f

MARLIN GULoRMsEN, HENRY Bonnnwroii.

